* Gravity: The Sun's immense mass exerts a strong gravitational pull on all the planets. This pull acts as an invisible tether, constantly drawing the planets towards the Sun.
* Inertia: Planets are moving objects and, according to Newton's first law of motion, they tend to continue moving in a straight line at a constant speed unless acted upon by a force. This tendency to keep moving in a straight line is called inertia.
How they work together:
1. Initial Motion: In the early solar system, planets formed from a swirling cloud of gas and dust. This rotation gave them an initial velocity.
2. Balance: The Sun's gravity pulls the planets inward, trying to make them fall into the Sun. But their inertia keeps them moving in a straight line, trying to fly off into space. The result is a compromise: the planets orbit the Sun in a curved path.
3. Stable Orbit: The balance between gravity and inertia creates a stable orbit. The planets don't fall into the Sun because their sideways motion keeps them from doing so. They don't fly off into space because the Sun's gravity keeps them bound.
Important Note: The orbits of the planets aren't perfectly circular, but slightly elliptical. This means the distance between a planet and the Sun varies slightly throughout its orbit.
